One of the maintenance problems associated with fuel nozzles is the scratching of its face occasioned by the face seal that prevents leakage of fuel and an escapement of flames from the engine's combustor. This scratching would otherwise prevent the reuse of the fuel nozzle. Heretofore the face was reworked by what is considered in today's standards a tedious, time-consuming procedure.
The heretofore solution was to remove the fuel nozzle and insert it into a fixture that was adapted to fit onto a grinding machine that included a fixed grinding wheel and a movable table. The fixture was locked onto the table and was shimmied in order to present the face of the nozzle in a horizontal position relative to the tangent at the point where the grinding wheel touched the face of the nozzle. The intent was to grind the face so that it would be substantially parallel to the diametrical pitch of the threaded portion of the nozzle that surrounded the face. Obviously, since the planes of the face were in spatial relationship and the shimming was a trial and error procedure, the set up of the fixture was a time-consuming task.
Because the grinding heretofore was done in a horizontal direction by passing the grinding wheel over a portion of the face in a rectilinear motion while traversing the grinding wheel until the entire face was finished, the face had to be lap finished. This necessitated removing the nozzle from the grinding machine so that a hand lapper could be employed to perform the lapping operation. Typically, this was performed by another operator in another department. The lapping machine was a hand-held device with a rotating wheel rotated by the operator that through a camming device imparted an oscillating motion to the spindle. A small replaceable and expendable disk shaped emery cloth was mounted on the end of the spindle adapted to bear against the face of the nozzle. The lapping operation was extremely time-consuming before the required finish on the face was realized.
I have found that I can obviate the cumbersome procedure noted in the above by providing a rotatable fixture having indexing means to square the face relative to the pitch diameter of the nozzle's threads. The fixture is adapted to fit on the same grinding machine that was heretofore utilized but the indexing and grinding operation eliminated the shimming and lapping operation. Because the grinding provided an acceptable finish thereby eliminating the lapping operation, the same results were achieved in a single operation rather than the two heretofore required. I have found that not only is there a substantial economical savings because of the invention, the time for reworking the face was reduced by twelve times. A typical time to rework a piece by the heretofore method was 6.5 hours as compared to 0.5 hours with the use of this invention.